go to Visualization|Plot Signals, a window will appear asking to set plotting parameters (such as samples, frequency range, number of channels, etc …). The The NBT signal viewer gives you many options for viewing your signals.

you might also want to visualize time-frequency and power spectrum plots for a single channel: go to Visualization|Plot time-frequency plot and power spectrum of one channel, a window will appear asking to set plotting parameters (such as samples, channel, select plot power or plot amplitude, etc. Click here for extended tutorial.)